Background: Positron emission tomography (PET) has been retrospectively reported to be a sensitive method for detecting malignant melanoma metastases.
Methods: One hundred consecutive patients with high risk melanoma (tumor thickness > 1.5 mm) were prospectively evaluated (52 at primary diagnosis, comprising Group A, and 48 during follow-up, comprising Group B) by whole-body PET and conventional diagnostics (CD).
Results: In Group A, the sensitivity of PET was 100% and the specificity was 94%, whereas CD did not identify any of the 9 lymph node metastases and demonstrated a lower specificity (80%). In Group B, 121 lesions were detected, 111 by PET and 69 by conventional imaging. On the basis of patients, the sensitivity, specificity, and accuracy of PET were 100%, 95.5%, and 97.9%, respectively (91.8%, 94.4%, and 92.1%, respectively, on the basis of single metastases). Prospectively, CD did not identify all patients with progression (sensitivity, 84.6%) and detected significantly fewer metastases (sensitivity, 57.5%) with much lower specificity (68.2% on the basis of patients, 45% on the basis of single lesions); therefore, the accuracy of CD was 77.1% on the basis of patients and only 55.7% on the basis of single metastases. Results also depended on specific sites: while PET yielded a higher sensitivity in detecting cervical metastases (100% vs. 66.6%) and abdominal metastases (100% vs. 26.6%), computed tomography proved to be superior in detecting small lung metastases (87% vs. 69.6%).
Conclusions: PET is a highly sensitive and specific technique for melanoma staging. With the exception of the brain, one single whole-body 18F-fluorodeoxyglucose-PET scan could replace the standard battery of imaging tests currently performed on high risk melanoma patients.